Pioneer 4 was a spin-stabilized spacecraft launched as part of the Pioneer program on a lunar flyby trajectory and into a heliocentric orbit making it the first U.S. probe to escape from the Earth's gravity. It carried a payload similar to Pioneer 3: a lunar radiation environment experiment using a Geiger-Müller tube detector and a lunar photography experiment. It passed within 60,000 km of the Moon's surface. However, Pioneer 4 did not come close enough to trigger its photoelectric sensor. The spacecraft was still in solar orbit as of 1969.
Read more about Pioneer 4: Spacecraft Design, Launching Vehicle, Mission
Famous quotes containing the word pioneer:
“The poet is no tender slip of fairy stock, who requires peculiar institutions and edicts for his defense, but the toughest son of earth and of Heaven, and by his greater strength and endurance his fainting companions will recognize the God in him. It is the worshipers of beauty, after all, who have done the real pioneer work of the world.”
—Henry David Thoreau (1817–1862)